B. N. Efremov

Nanosize catalysts based on carbon materials promoted by cobalt tetra(para-methoxyphenyl) porphyrin pyropolymer for oxygen electroreduction

We present the results of electrochemical and structural investigations of several carbon materials: carbon blacks AD 100 and XC 72, ultradisperse diamond (UDD), multiwalled nanotubes (MWNT), various types of filament-like carbon materials (CFC series), and similar carbon materials promoted with cobalt tetra(para-methoxyphenyl) porphyrin (CoTMPhP) pyropolymer (PP). The electrochemical studies were performed at room temperature in 0.5 M H2SO4 by using a rotating disk electrode (RDE), a rotating ring-disk electrode (RRDE) (a thin layer of test material was applied onto the disk electrode), and a floating electrode. Structural characterization of initial and promoted carbon materials involved the determination of specific surface area by the BET method and by the polarization capacitance from cyclic voltammograms, and the particle morphology and dimensions by the transmission electron microscopy (TEM) method. The study of kinetics and mechanism of oxygen electroreduction on carbon materials promoted with CoTMPhP PP showed that the catalysts based on carbon materials of CFC and UDD series possess high specific activity in this reaction and high selectivity with respect to oxygen reduction to water. These catalysts are superior to the catalysts, in which carbon blacks AD 100 and XC 72 are used as the supports, in the specific activity.

Electroconductance and Penetrability of Polybenzimidazole Membranes in Alkaline Solutions

Effect of various factors on the conductance and penetrability of polybenzimidazole membranes is studied. The conductivity of alkali-doped membranes is no lower than 0.01 S cm–1. The membrane penetrability to methanol is close to that of Nafion.

Electroreduction of Oxygen in the Presence of Tyrosinase Adsorbed on Carbon Materials

Electroreduction of oxygen on carbon materials with immobilized tyrosinase is studied, and the effect the carbon support nature and the immobilization technique have on the reaction rate is determined. The tyrosinase activity in a direct bioelectrocatalysis is shown to be lower than that of another copper-containing enzyme, laccase. A maximum activity is obtained when covering the carbon surface with a composite based on tyrosine, tyrosinase, and Nafion.

Effect of Partial Pressure of Oxygen on Its Bioelectrocatalytic Reduction at a Laccase-Nafion Composite

Dependences of the rate of bioelectrocatalytic reduction of oxygen at an electrode with a laccase–Nafion composite on the partial oxygen pressure are obtained in a wide potential range. The saturation concentration by oxygen for this enzyme electrode is 0.98 mM and the solution stirring tells only at low partial oxygen pressures. The Michaelis constants and catalytic constants are compared in conditions bioelectrocatalysis and enzymic catalysis.